1. Field of the Invention
The present invention relates to packet switching method and system and more particularly to packet switching method and system in a packet network comprising a plurality of nodes each including a self-routing switch.
2. Description of the Related Art
It has hitherto been known of transit nodes in the network that there are available a switching station for switching a channel of each call and a cross-connect for semi-fixed connection of paths each having bundled unidirectional channels as described, for example, on pages 13-18 of "Institute of Electronics, Information and Communication Engineers Technical Report, Vol. 88, No. 131, IN88-32-45" Jul. 20, 1988.
Features of each transit node can be summarized as follows:
(1) The switching station has a call processing processor and for each call, translates a terminating address to determine an optimum route.
(2) In the cross-connect, the path is semifixedly established and the cross-connect does not have such a control function for each call as possessed by the tandem station. In a network of ATM (asynchronous transfer mode), the cross-connect transfers an inputted ATM cell to a path selected in accordance with a VPI (virtual path identifier) contained in the inputted cell.
In the network using the switching station as the transit node, routing is carried out for each call and therefore the thus constructed network is highly efficient. However, if all transit nodes are constructed of switching stations, the processing load applied, for call terminating process, on each transit node is increased.
On the other hand, in the network using the cross-connect as the transit node, each cross-connect does not require any processor for call processing and hence reliability of the network as a whole can be improved. However, the path for which the capacity is secured in advance must be established semi-fixedly, thus decreasing utilization efficiency of network resources. More specifically, as compared to the network using the switching station as the transit node, the network cost is disadvantageously increased for the same performance (call block rate) and the call block rate is increased for the same network construction.